Name: Kat Pierce ID Number: 1461881 Section: BX Lab Partner: John Redfield Chem 142 Experiment #3: Calibration Curves and an Application of Beer's Law By signing below, you certify that you have not falsified data, that you have not plagiarized any part of this lab report, and that all calculations and responses other than the reporting of raw data are your own independent work. Failure to sign this declaration will result in 5 points being deducted from your report score. Signature: Note: All sections of this report must be typed Total Points = 55 pts (10 pts notebook, 45 pts template) DATA, GRAPHS AND CALCULATIONS Creating the calibration curve: lmax: 470 nm 2 pt Ferroin: Concentration (M) 1.25 x 10^-5 2.50 x 10^-5 3.75 x 10^-5 5.00 x 10^-5 6.25 x 10^-5 Absorbance 0.120 0.186 0.320 0.432 0.560 Absorbance vs.your Concentration Place your calibration plot here. Make plot big enough to cover this instruction box so that it is large enought for someone else to read. 0.6 y = 9008x - 0.0142 R² = 0.9903 This calibration plot is Abs vs. concentration of ferroin (M) (y-axis vs. xaxis)0.5 4 pts Absorbance Use the 0.4 online resources if you need help figuring out how to plot a graph in Excel. 0.3 Title the graph and label the axis, including the correct units (Absorbance data is unitless). Be sure to double check your units and 0.2 formatting once you print the report. 0.1 Add a Trendline to show the linear fit of your data. Choose a linear line andchoose the options that will "display the equation on the chart", 0 including the R2 value. 0 0.00001 0.00002 0.00003 0.00004 0.00005 0.00006 0.00007 Concentration of ferroin (M) Slope of Absorbance versus concentration graph -1 9008 M y-intercept of Absorbance versus concentration graph -0.0142 2 pts Detailed calibration equation: y = 9008x -0.0142 2 pts (review the introductory information in the lab manual for an explanation of what is meant by a "detailed" calibration equation) Determining the Amount of Iron in an Iron Tablet 3 pts 1) Average mass of a tablet 436 mg 2) Mass of crushed tablet used in analysis 20 mg 3) Final volume after filtered crushed tablet solution is diluted in volumetric flask (lab manual Part II, Step 5) 100 mL 4) Volume of diluted crushed tablet solution 5 transferred to the new volumetric flask (lab manual Part II, Step 6) mL 5) Final volume of ferroin complex solution (lab manual Part II, Step 9) mL 6) Absorbance of the ferroin complex solution (lab manual Part III, Step 3) 7) 100 0.051 Using the calibration equation and the absorbance you measured for the prepared sample, calculate the ferroin concentration. Show your work and don't forget to include units. Abs = (slope x concentration) + y-intercept 0.051 = (9008 x concentration) - 0.0142 0.652 = 9008 x concentration 0.652 abs / 9008 = 7.24x 10^-6 M ferroin concentration 8) 3 pts Based on the procedural steps and the ferroin concentration you just calculated, calculate the moles of ferroin in the final ferroin complex solution prepared in Part II, Step 9. Show your work, including units. mol = M X V M of ferroin: 7.24x10^-6 M V = 100 mL of ferroin complex solution x 10^-3 = 0.1 L 7.24x10^-6 M x 0.1 L = 7.24x10^-7 moles of ferroin 9) 3 pts Based on the moles of ferroin in the final ferroin complex solution, calculate the moles of iron in the crushed tablet solution prepared in Part II, Steps 2-5. Show your work, including units. ferroin ion: Fe2+ in complex = 1:1 ratio 7.24x10^-7 moles of ferroin x 20.0 dilution factor = 1.45x10^-5 moles of iron in the crushed tablet soln 10) Using the "moles of iron in the crushed tablet solution" you just calculated, calculate the mass (in mg) of iron in the crushed sample that you weighed out. Show your work, including units. 1.45x10^-5 moles of iron x (55.845 g Fe/1 mol) = 8.087x10^-4 g of Fe 8.087x10^-4 g of iron x (1000 mg/1 g) = 0.809 mg of Fe 11) 3 pts From the mass of iron in the crushed tablet sample you weighed out, calculate the mass (in mg) of iron in a whole tablet. Show your work, including units. 0.809 mg of Fe crushed tablet x (436 mg average mass of tablet)/27 mg of iron per tablet on bottle= 13 mg of iron in whole tablet 12) 3 pts mg of iron per tablet (as listed on the bottle) Results and Discussion 27 mg 3 pts Results and Discussion 1. Compare your mass of iron per tablet with the amount listed on the bottle label. Calculate the % error and discuss YOUR major sources of error. (4 pts) % error = measured-true/true x 100 % error = 13 - 27 / 27 x 100 % error = 52% Our biggest source of error may have been the readings from the colorimeter. Because of it's age it may have affected the colorimeter's accuracy. Another source of error may have been when we put the beaker of HCl, water and iron tablet on the hot plate, we didn't take it off to let it cool. We just let the hot plate cool with the beaker still on top. This could have affected the cooling process and it also caused a lot of the solution to evaporate. 2. If you did not wait for the complete formation of the ferroin complex in Part II, step 10, how would your Abs data be different? Explain how would this affect your determination of the mass of iron in the tablet? (4 pts) If you do not wait for the ferroin complex formation to complete, then the absorbance will be less. If the process of the formation does not finish, then the concentration of ferroin will not be accurate. Without an accurate concentration, you cannot calculate an accurate absorbance. You cannot determine the mass of iron in the tablet without knowing the ferroin concentration or absorbance. 3. You use atomic emission spectroscopy, another spectroscopic technique, to measure the Li+ concentration in 5 standard solutions of varying concentrations of LiCl. The intensities for the standard solutions are plotted versus the concentrations and the resulting calibration equation is: Intensity = 83,100 M-1 * [Li+] + 1.65 If the intensity of your unknown sample is 101, what is the concentration of Li+ in the analyzed sample? (4 pts) Intensity = 83,100 M^-1 * [Li^+] + 1.65 101 = 83,100 M^-1 * [Li^+] + 1.65 99.35 = 83,100 M^-1 * [Li^+] 99.35/ 83,100 M^-1 = 0.001195 M [Li+] = 0.001195 M If 15 mL of the original unknown sample was diluted to 350. mL prior to analysis, what is the concentration of Li+ in the original solution? (4 pts) 0.001195 M x (0.35 L/0.015 L) = 0.028 M [Li+] Laboratory Waste Evaluation (1 pt) Laboratory waste is considered anything generated during an experiment that is disposed of down the sewer drain, thrown in the garbage, collected in a container for disposal by the UW Environmental Health & Safety department, or released into the environment. Based on the written lab procedure and your actions during the lab, list the identity and approximate amount (mass or volume) of waste that you generated while performing this experiment. 10 kim wipes 5 mL of 6.25x10^-4 M ferroin stock soln 10 mL volumtetric flask with DI water x 5 = 50 mL of DI water 220 mL of water 2 mL of 0.1 M HCl 2 mL of 0.23 M hydroxylamine hydrochloride 1 mL of 1.0 M sodium acetate soln 3 mL of 3.6x10^-3 M 1,10-phen 1 pipettor tip 2 disposable pipettors Concentration 0.0000125 (M) (x 10-5) 0.000025 0.0000375 Absorbance 0.12 0.186 0.32 0.00005 0.0000625 0.432 0.56 Absorbance vs. Concentration 0.6 y = 9008x R² = 0.9903 Absorbance 0.5 0.4 0.3 0.2 0.1 0 0 0.00001 0.00002 0.00003 0.00004 0.00005 Concentration of ferroin (M) s. Concentration y = 9008x - 0.0142 R² = 0.9903 0.00004 0.00005 0.00006 0.00007 ation of ferroin (M)